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From Michael Baessler <...@michael-baessler.de>
Subject Re: PEAR installer and required external resources
Date Sat, 17 Feb 2007 10:00:16 GMT
Marshall Schor wrote:
> greg@holmberg.name wrote:
>> Here's an apparent catch-22 about installing PEAR files that I don't 
>> quite
>> understand.
>>
>> How is installation supposed to work when there's a configuration 
>> parameter
>> or external resource in the component descriptor that is both 
>> required and
>> doesn't have a default value?
>>
>> For example, I have one external resource that is the name of a 
>> certain file
>> you want the annotator to use (it's some static reference data).  
>> This is
>> required--the annotator can't operate without it.  And there can be no
>> reasonable default--we can't guess the name of the file the customer 
>> will
>> want to use when we create the component descriptor.
>>   
>
> What is suggested here is to include a dummy version of the static 
> reference data as a resource.  Then set the parameter to reference 
> that resource.   Of course, after "install", the user will need to 
> configure this to their actual data file.
>> So the user installing the PEAR file really must set it to something 
>> before
>> running the annotator.
>>
>> So I bound a path that works on my development machine.  However, on 
>> the customer's' machine this fails when installer attempts verify the 
>> component
>> by loading the annotator classes and calling initialize():
>>
>>     com.ibm.uima.resource.ResourceInitializationException:
>>     Could not access the resource data at
>>     file:/C:/blah/blah
>>   
>
> You want to bind a path that is a resource in the PEAR, and then use 
> the $macro capabilities to have that path adjusted at install time to 
> take into account where it was installed.
>> I tried just leaving the resource unbound, but first the component 
>> editor
>> complains ('There is no resources satisfying the required resource 
>> dependency
>> with key "blah.blah.blah"'), and then during installation I get the same
>> ResourceInitializationException.
>>
>> I also tried binding it to a URL that doesn't exist, but the component
>> editor complains about that too ('Could not access the resource data
>> at blah'), and then the installer throws ResourceInitializationException
>> again.
>>
>> A similar thing happens with configuration parameters that are required
>> and not defaulted, it just happens later in the installation process,
>> when you try to run the AE in the CVD, and the call to process() 
>> fails when
>> our software throws an exception about the missing value.
>>   
>
> Right - to get this to pass validation, you have to have some defaults.
>> At least with configuration parameters there's a opportunity in the 
>> install
>> process between pushing "Install" and "Run your AE in the CAS Visual
>> Debugger" to edit the descriptor file.  But there's no such opportunity
>> with the required external resources, since verification happens 
>> immediately
>> after the files are extracted from the PEAR file.
>>
>> What is the intended path of sucess here?  It doesn't seem possible.
>>
>> It seems to me that the installation process needs a step between 
>> extraction
>> and verification in which the user can configure the AE by editing the
>> descriptor (either in a text or XML editor, or in the Eclipse Component
>> Descriptor editor).
>>   
>
> This is a good suggestion for an enhancement. Absent this enhancement, 
> will the approach outlined abouve work in your situation?
I also think that this will be a good enhancement for the PEAR installer 
GUI.

If all the suggestions above doesn't work, besides the PearInstaller GUI 
there is also a PEAR API that can be used to install pear files to a system.
With the PEAR API you can specify if you only want to install the pear 
or if you additionally want to verify it.  With this, you
can provide your own "pear installer" that is integrated to your 
application. For more details about the PEAR API please refer to the
documentation (chapter 6.2 in the references book) where you will also 
find a short example.

-- Michael



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